The present invention relates to molding materials having improved processing properties and to aging-resistant plastic sheets produced from these materials, in particular flexible deep-drawing sheets having improved aging behavior.
A very wide variety of webs and laminated sheets are known, such as those based on acrylonitrile/butadiene/styrene copolymers with plasticizer-containing polyvinyl chloride (PVC), laminated with rigid and soft PVC. Because of their plasticizer content, these sheets are considered to have the disadvantages that their resilience and low-temperature flexibility gradually declines over time; and that, on prolonged exposure to heat and light, even cracking of the surface can result.
On the other hand, rigid or hard polymers, such as rigid PVC have the disadvantage of great stiffness and poor low-temperature flexibility.
Yet heat-resistance and resistance to aging on exposure to light are critical performance characteristics for sheets, in particular deep-drawing sheets, for automobile trim components. The flexible but readily thermoformable trim panels, particularly used for dashboards, that contain acrylonitrile/butadiene/styrene, polyvinyl chloride and plasticizer components are relatively sensitive to oxidation, due to the sensitivity of their diene structure to oxidation effected by exposure to light energy and/or heat energy, and therefore fail also fully to meet the requirements of heat- and aging-resistance.
West German patent application No. P 33 42 435.7 discloses molding materials and sheets comprising (1) 45-90% by weight, preferably 50-85% by weight, of a polyvinyl chloride that is grafted with acrylate and that has an acrylate content of 30-60% by weight preferably 35-50% by weight (based on 100 parts by weight of PVC); and (2) 10-55% by weight, preferably 15-50% by weight, of another polymer or polymer blend that has a glass transition temperature greater than 70.degree. C., preferably greater than 80.degree. C., and is compatible with the PVC graft polymer. However, this broad class of disclosed molding materials and sheets, respectively, is not very advantageous in conjunction with soft foams and, for example, is not characterized by good contact characteristics.